The present invention relates generally to diffractive multifocal ophthalmic lenses. In particular, the present invention is an ophthalmic lens manufactured from hydrogel materials and a method for ultrasonically welding the lens.
Ophthalmic lenses are used to correct vision impairments, and can be embodied in a number of forms. Contact lenses and surgically implanted intraocular lenses are probably the most common. Other ophthalmic lenses include artificial corneas and intralamellar implants. These lenses are often manufactured from silicone, polyurethane, hydrogel and other polymers. Known fabrication techniques include grinding, lathe cutting, compression molding, injection molding and cast molding. Ophthalmic lenses of these types, as well as materials from which they can be fabricated and methods of manufacture, are disclosed generally in the following references:
______________________________________ U.S. PATENTS 4,664,666 Barrett 4,702,865 Koziol et al 4,618,649 Ofstead 4,693,939 Ofstead 4,771,089 Ofstead 4,828,558 Kelman 4,642,112 Freeman 4,731,078 Stoy et al 4,340,283 Cohen FOREIGN PATENTS European Patent 43640 Polmanteer et al. U.K. Patent 1,154,360 Hofmann et al. European Patent Appln. 0 188 110, Published July 23, 1986. U.K. Patent Publication 2,171,106 Tahan ______________________________________